Wednesday, October 30, 2013

Weight and Risk of Death

Weight is not the best predictor of death risk, especially when your weight does not fall into an extreme.

That was a key point during a recent talk I gave (featured in last week's post) on the value of weight and waist-to-hip ratio to serve as health and longevity assessments.

This is supported by the work of Dr. Katherine Flegal, who looked at a series of studies known as The National Health and Nutrition Examination Surveys (NHANES) [1]. Each study featured four-to-six-year samples of the United States, with each sample being representative of the whole US population in terms of sex and race percentages.

Dr. Flegal combined the data from all three study periods to find out the risk of death according to age and weight. The results are shown in the table below, with the percentages showing the likelihood of death when compared to the "healthy" group.

Weight Group
25-59 Years
Very Lean

Very Obese
*Weight groups feature people who have never smoked and weights are assessed by 
body mass index, or BMI.

As you see, the very lean and very obese groups have higher death rates during all age ranges. Specifically, sexagenarians who are very lean or very obese face a much greater death risk.

On the other hand, overweight individuals have lower death rates in all age groups, and the risk associated with obese individuals differs between age groups and is only 13% greater for those who are at least 70 years of age (keep in mind that BMI does not account for the differences in fat mass versus lean mass, so a portion of those in the overweight group likely fall into this group due to an above average amount of muscle and bone tissue).

What does all of this mean? When not falling into an extreme, weight is a poor way to predict how long you will live. In general, weight is a poor way to assess health. As I have discussed before, not all body fat is bad, and habits are much more important to health than size/weight

At almost any weight, if you develop healthy habits, you will achieve health.

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